Synthesis and reactivity of nonbridged metal-metal bonded rhodium and iridium phenanthroline-based N2O2 dimers

Article abstract of DOI:10.1021/om010903g

Nonbridged metal dimers of phenanthroline-based N₂O₂ ligands of rhodium and iridium have been synthesized from the reactions of metal hydrides with TEMPO (2,2′,6,6′-tetramethylpiperidinyloxy). Modification of phenathroline ligands ha

Full text of DOI:10.1021/om010903g

Organometallics 2002, 21, 2743-2750
2743
Syn th esis a n d Rea ctivity of Non br id ged Meta l-Meta l
Bon d ed Rh od iu m a n d Ir id iu m P h en a n th r olin e-Ba sed
N2O2 Dim er s
Maoqi Feng and Kin Shing Chan*
Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
Received October 16, 2001
Nonbridged metal dimers of phenanthroline-based N2O2 ligands of rhodium and iridium
have been synthesized from the reactions of metal hydrides with TEMPO (2,2′,6,6′-
tetramethylpiperidinyloxy). Modification of phenathroline ligands has led to more lipophilic
metal complexes. The oxidative additions of the metal dimers with methyl iodide, silane,
and hydrogen have been studied.
Nonbridged d7-d7 dimeric metal-metal bonded com-
plexes of rhodium1-15 and iridium16-20 have attracted
considerable interest owing to their rich chemistry and
unique structural features. The fairly extensive chem-
istry of the nonbridged metal-metal bonded complexes
is exemplified by the porphyrin ligand class. This class
of metal porphyrin dimer complexes, especially that of
rhodium, undergo facile dissociation to yield extremely
reactive metal-centered radicals. These rhodium mono-
mers undergo halogen abstraction,21 olefin insertion,21
novel carbon-hydrogen bond activation, especially the
activation of methane,22-25 and carbon-carbon bond
activation by sterically hindered rhodium porphyrin
monomers.19c Electrocatalytic reduction of oxygen via
a four-electron process catalyzed by iridium porphyrins
has also been reported.17,20
The rhodium porphyrin chemistry has been extended
to complexes with nonmacrocyclic ligand systems which
have the potential to manifest more versatile reaction
pathways and thus faster substrate reactions than those
observed for rigid tetradentate macrocyclic com-
plexes.26-30 Wayland et al. reported the synthesis and
the chemistry of [N,N′-ethylenebis(3,5-di-tert-butylsali-
cylaldiminato)]rhodium(II) dimer, [(ttbs)Rh]2, with H2,
CO, and CH2dCH2.26,27 Eisenberg and co-workers re-
ported that the tetradentate dianionic Schiff base ligand
H2bu4 (salophen) reacts with [RhCl(C2H4)2]2 and
NR4OH (R ) n-Bu, Et) to produce the complexes RhR-
(bu4salophen) (R ) n-Bu, Et), which undergo photoly-
sis under a hydrogen atmosphere to generate RhH-
(bu4salophen) and the corresponding alkanes.28,29
1,10-Phenanthroline (Phen) with phenolic moieties at
2,9-positions bearing a similar N2O2 donor set is a
relatively unexplored N2O2 system.31 Compared to the
Schiff base, bearing relatively sensitive imine bonds,32
the phenanthroline skeleton is less susceptible to de-
composition by redox reaction and hydrolysis due to its
more robust pyridine ring.33 Therefore, their metal
complexes may be more robust and efficient reagents
and catalysts. We now report the synthesis and chem-
istry of these rhodium and iridium nonbridged metal-
metal bonded dimers of 1,10-phenanthroline type N2O2
ligands (Figure 1).
(1) Collman, J . P.; Arnold, H. J . Acc. Chem. Res. 1993, 26, 586.
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Clarendon Press: Oxford, 1993.
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Feng, M.; Chan, K. S. J . Organomet. Chem. 1999, 584, 235. (c) Tse,
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hedron Lett. 1982, 23, 5291.
(33) (a) Lam, F; Chan, K. S.; Liu, B.-J . Tetrahedron. Lett. 1995, 36,
6261. (b) Lam, F.; Feng, M.; Chan, K. S. Tetrahedron 1999, 55, 8377.
10.1021/om010903g CCC: $22.00 © 2002 American Chemical Society
Publication on Web 05/22/2002

2744 Organometallics, Vol. 21, No. 13, 2002
Feng and Chan
(eq 4).37 The corresponding Kumada coupling36 with
Grignard reagents was less effective.
F igu r e 1.
Resu lts a n d Discu ssion
The synthetic routes of two N2O2 ligands, 9-bis(5-tert-
butyl-2-hydoxyphenyl)-1,10-phenanthroline (H2bpp, 6a)33
and the more lipophilic 2,9-bis(5-tert-butyl-2-hydoxy-
phenyl)-5,6-di-n-butyl-1,10-phenanthroline (H2bbpp, 6b),
are shown in Scheme 1. The synthesis of the N2O2
ligand H2bpp [2,9-bis(5-tert-butyl-2-hydoxyphenyl)-1,10-
phenanthroline followed a modified Sauvage procedure
for the preparation of 2,9-disubstituted phenanthro-
lines.31 Nucleophilic addition of the lithium reagent
2-bromo-1-methoxyl-4-tert-butylbenzene 3 to 1,10-phenan-
throline followed by oxidation with manganese dioxide
yielded 5a in 80% yield. Demethoxylation with pyri-
dinium hydrochloride gave H2bpp 6a in 80% yield.
Since the lipophilicity of the N2O2 ligand is important
for studying the chemistry of their metal complexes, a
more lipophilic derivative was prepared. As the more
convenient incorporation of an alkyl group in the phe-
noxy groups was found to be less effective in enhancing
the solubility, functionalization of 1,10-phenanthroline
for the preparation of alkyl Phen was sought. 2,9-Bis-
(5-tert-butyl-2-hydoxyphenyl)-5,6-di-n-butyl-1,10-phenan-
throline ligand (H2bbpp, 6b) was chosen as the target
with alkyl groups introduced at the 5- and 6-positions.
For positions 3 and 8, alkyl groups introduced will
hamper the synthesis of the N2O2 ligand at the subse-
quent nucelophilic substitution step due to steric hin-
drance. For positions 4 and 7, alkyl groups have been
introduced.34 The synthesis however is very lengthy.
Positions 5 and 6 are the most ideal as 5,6-dibromo-
Phen 7 is conveniently prepared from Phen via bromi-
nation.35 Furthermore, the substituent electronic effect
is too remote to affect the chemistry at the N2O2 core.
5,6-Dibutyl-Phen was prepared by a bromination/
cross-coupling route. 5,6-Dibromo-Phen 7 was synthe-
sized in 65% yield by the improved bromination of Phen
with Br2 in oleum at 120 °C for 12 h in a sealed tube
(eq 1). In an open system,35 a much lower yield of only
The synthetic route of 2,9-bis(5-tert-butyl-2-hy-
doxyphenyl)-5,6-di-n-butyl-1,10-phenanthroline ligand
(H2bbpp, 6b) is shown in Scheme 1. The aryllithium
reagent of 3 underwent nucleophilic substitution at the
2,9-positions of 5b after oxidative re-aromatization to
produce 5b in 75% yield. 5b was then demethylated
with py‚HCl at 210 °C for 4 h to produce 6b in 85% yield.
Meta la tion s of Liga n d s. Rh(bpp)Cl 8a , Rh(bbpp)-
Cl 8b, Ir(bpp)(CO)Cl 9a , and Ir(bbpp)(CO)Cl 9a were
synthesized by the metalation of H2bpp 6a and H2bbpp
6b with RhCl319,38 and [Ir(COD)2Cl]239 in 42, 36, 38, and
34% yield, respectively (eqs 2 and 3). The solubilities of
the metal complexes of bpp were found to be poor in
most organic solvents, while that of bbpp was much
better. For example, 8a and 8b dissolved sparingly in
CHCl3, while 9a and 9b dissolved well.
IR streching frequencies of CO groups in Irbpp(CO)-
Cl 9a and Irbbpp(CO)Cl appeared at 2049 and 2052
cm-1, suggesting little difference in the electronic
property of the ligands.
Syn th esis of M(L)R (M ) Rh , Ir ). M(L)R (L ) bpp,
i
bbpp; M ) Rh, Ir(CO); and R ) Me, Pr) were synthe-
sized by the reductive alkylation of M(L)Cl with NaBH4/
RX (eq 4).40 Upon addition of NaBH4, the orange
suspension of Rh(L)Cl and Ir((L)(CO)Cl changed into
intense deep brown in color, which indicated the suc-
cessful reduction of RhIII and IrIII into RhI and IrI,
(34) Kern, J .-M.; Sauvage, J .-P.; Weidmann, J .-L. Tetrahedron 1996,
52, 10921.
(35) Mlochowski, J . Roczniki Chemii. Ann. Soc. Chem. Polonorum
1974, 48, 2145.
(36) Diederich, F., Stang, P. J ., Eds. Metal-catalyzed Cross-coupling
Reactions; Wiley-VCH: New York, 1998.
(37) Tzalis, D.; Knochel, P. Tetrahedron Lett. 1999, 40, 3685.
(38) (a) Zhou, X.; Wang, R.-J .; Mak, T. C. W.; Chan, K. S. Inorg.
Chim. Acta 1998, 270, 551. (b) Zhou, X.; Wang, R.-J .; Xue, F.; Mak, T.
C. W.; Chan, K. S. J . Organomet. Chem. 1999, 580, 22. (c) Zhou, X.;
Tse, M. K.; Wu, D.-D.; Mak, T. C. W.; Chan, K. S J . Organomet. Chem.
2000, 598, 80.
(39) Ogoshi, H.; Setsune, J .-I.; Yoshida, Z. J . Organomet. Chem.
1987, 159.
(40) Ogoshi, H.; Setsune, J .; Omura, T.; Yoshida, Z. J . Am. Chem.
Soc. 1975, 97, 6461.
30% was obtained. 5,6-Dibromo-Phen 7 then underwent
Negishi cross-coupling36 with BuZnBr catalyzed by
PdCl2(PPh3)2 to yield 5,6-dibutyl-Phen 4b in 28% yield

Rh and Ir Phenanthroline-Based N2O2 Dimers
Organometallics, Vol. 21, No. 13, 2002 2745
Sch em e 1
respectively. Subsequent oxidative addition with alkyl
halides produced metal alkyls (eq 4).
In the H NMR spectrum, the Rh-CH3 resonance in
appeared at -22.04 ppm in DMSO-d6 added with
CF3SO3H.41 CF3SO3H was necessarily added to prevent
M(bpp)H from dissociation into M(bpp) anion, which
may lead to decomposition.42 The hydride peak of
Rh(bppp)H 15b appeared as a doublet at -20.27 ppm
1
Rh(bpp)Me 10a appeared at 0.51 ppm in DMSO-d6 with
J Rh-H equal to 2.4 Hz. The Ir-CH3 resonance in Ir(bpp)-
Me 10b appeared at 0.04 ppm in DMSO-d6. The chemi-
with J
) 44.4 Hz in CD3OD-d4 added with a small
Rh-H
i
cal shifts of the Pr group in Rh(bpp)iPr 11a were -0.55
amount of CF3SO3H. The hydride peak of Ir(bbpp)H 16b
appeared at -20.23 ppm in CD3OD-d4. The solubilities
of the metal hydrides of the bbpp ligand were much
better without the need of polar DMSO solvent.
The N2O2-metal hydrides exibihited typical insertion
and coordination chemistry. Styrene reacted with
Rh(bpp)H 14a in THF to give the addition product of
Rh(bpp)(CH2CH2Ph) 17a quantitatively (eq 7). Ir(bpp)H
15a formed a six-coordination adduct with PPh3 in
DMSO-d6. The hydride singlet appeared at -22.04 ppm
and was split into a doublet with J P-H ) 15.8 Hz (eq 8).
(dCH-) and -0.07 (CH3), and those in Ir(bpp)iPr 13a
were -0.85 (dCH-) and -0.67 (CH3). The methyl signal
of Rh-CH3 in Rh(bbpp)Me 10b appeared at 0.51 ppm
in CDCl3 with J Rh-H equal to 2.1 Hz. The methyl signal
of Ir-CH3 in Ir(bbpp)Me 12b appeared at 0.35 ppm in
CDCl3. These chemical shifts and coupling constants are
similiar to that of close anaologues of Rh(SB)Me(py) (SB
) N,N′-ethylenebis(salicylideneiminato))41 with the
103Rh-H
Rh-CH3 appearing at 1.3 ppm [(CD3)2SO] and J
) 3.0 Hz.
The five-coordinate square planar complex M(L)R
readily formed a six-coordinate complex with ligands.
PPh3 reacted with Rh(bpp)Me 10a to give Rh(bpp)Me-
(PPh3) 14 in DMSO-d6 with the doublet of the methyl
signal changed into a double doublet in the 1H NMR
spectrum (eq 5). Furthermore, the 31P NMR showed that
a doublet appeared at 47.39 ppm with J Rh-P ) 138 Hz.
Syn th esis of M2(bp p )2 (M ) Rh , Ir ). Three general
methods exist for synthesizing rhodium and iridium
metal-metal bonded complexes: (i) photolysis of metal
alkyls;19 (ii) aerobic oxidation of rhodium hydride;6,7 and
(iii) reaction of metal hydride with TEMPO (2,2,6,6-
tetramethylpiperidine-1-oxyl).19a,b The first method usu-
ally requires long reaction time and is highly dependent
on both the quantum yields of the metalloporphyrin
alkyls and the experimental conditions. The second
method is difficult because overoxidation of the air-
sensitive metal-metal bonded dimer is possible. The
third one is the most convenient and efficient since it
is high yielding and excess TEMPO and TEMPOH
coproduct are easily removed by vacuum evaporation.19a,b
M2(L)2 were synthesized in high yields by the reaction
of M(L)H with TEMPO (eq 9). The chemical shifts of
Syn th esis of M(L)H. Syntheses of M(L)H (M ) Rh,
Ir) were accomplished by the reductive protonation of
M(L)Cl with NaBH4/H+ (eq 6). The characteristic IR
stretching frequencies of Rh-H and Ir-H fell at 2225
and 2046 cm-1, respectively, without any significant
electronic effect exerted by the ligands.
In the 1H NMR spectrum, the hydride peak of Rh-
(bpp)H 14a appeared as a doublet at -22.85 ppm with
J Rh-H ) 37.3 Hz. The hydride peak of Irbpp(H) 15a
(41) Cozens, R. J .; Murray, K. S. Chem. Commun. 1970, 1262.

2746 Organometallics, Vol. 21, No. 13, 2002
Feng and Chan
the metal-metal bonded dimers of nonmacrocylic lig-
ands are very distinctive. As DMSO used in NMR
analysis is a coordinating solvent, formation of com-
plexes with a metal-metal dimer is possible. Further-
more, two coordination modes of either O- or S-bonded
ligands are feasible. Infrared spectra have been utilized
in distinguishing between O- and S-bonded ligands.43
DMSO solvent likely coordinated to the Rh dimer as in
Rh2(O2CCH3)4(Me2SO)2 with sulfur as the donor atom,
have been synthesized from the reactions of metal
hydrides with TEMPO. Modification of phenanthroline
ligands has led to more lipophilic metal complexes. The
oxidative additions of the metal dimers with methyl
iodide, silane, and hydrogen have been successfully
carried out.
Exp er im en ta l Section
which was indicated by an upward shift of νSO (νS-O
)
All manipulations were performed under nitrogen by vacuum
line techniques or in a Braun MB 150 M glovebox. 1H NMR
spectra were recorded on either a Bruker DPX-300 (300 MHz)
or a Bruker AMX-500 (500 MHz) spectrometer. Chemical shifts
(δ) were reported with reference to the residual CHCl3 (δ 7.24
ppm) in CDCl3 or DMSO (δ 2.49 ppm) in DMSO-d6. 13C NMR
spectra were recorded on a Bruker DPX-300 (75 MHz) spec-
trometer. 31P NMR spectra were recorded on a Bruker AMX-
500 (H3PO4 was used as internal standard) spectrometer. The
coupling constants (J ) are reported in hertz (Hz). Low-
resolution mass spectra were recorded on a VG7070F mass
spectrometer. High-resolution mass spectra were recorded on
a Bruker APEX 47e FT-ICR mass spectrometer. IR spectra
were obtained on a Perkin-Elmer 1600 FT-IR spectrophotom-
eter. UV-vis spectra were recorded on a Hitachi U-3300
spectrophotometer. Yields were reported in either isolated
yield or NMR yield using the residue solvent proton as the
internal standard.
1086 cm-1, for free DMSO, νS-O ) 1050 cm-1 44). From
the IR spectrum, the peak at 1086 cm-1 was assigned
to the coordinated S-O stretching frequency in
DMSO-d6 solution of Rh2(bpp)2 19a . The S-O stretching
frequency was red-shifted by 36 cm-1 in DMSO. In the
case of Ir2(bpp)2 20a , the coordination mode of DMSO-
d6 was the same as that of Rh2(bpp)2 20a because the
S-O stretching frequency appeared at 1085 cm-1
.
Rea ction s of M2(L)2. M2(L)2 underwent character-
istic oxidative addition with MeI, Et3SiH, and H2.
Rh2(bpp)2 19a reacted with MeI to yield Rh(bpp)Me 12a
and Rh(bpp)I 25a in 32% and 28% yield, respectively
(eq 10). Rh2(bpp)2 19a reacted with Et3SiH to produce
Rh(bpp)(SiEt3) 21 and Rh(bpp)H 15a in 42% and 36%
yield, respectively (eq 11). Rh2(bpp)2 20a and Ir2(bpp)2
20b reacted with H2 to produce Rh(bpp)H 15a and
Ir(bpp)H 16a both in 90% yield (eq 12).
2,9-Bis(5-ter t-bu tyl-2-m eth oxyph en yl)-1,10-ph en an th r o-
lin e (5a ).33 The anisole 3 (15.5 g, 0.064 mol) in anhydrous
ether (20 mL) was transferred slowly to dried freshly cut
lithium metal (0.98 g, 0.14 mol) in anhydrous ether (10 mL)
via a cannula. The mixture was refluxed for 1 h under
nitrogen, and the aryllithio reagent was then transferred
dropwise to 1,10-phenanthroline (1.44 g, 8.0 mmol) in anhy-
drous toluene (15 mL) via a cannula under nitrogen to give a
red solution. The mixture was allowed to stir for 48 h at 40
°C. the solution was then cooled to 5 °C, and water (30 mL)
was added under nitrogen to hydrolyze the reaction mixture.
The organic layer was collected, and the aqueous layer was
extracted with CH2Cl2. MnO2 (5.0 g, 57 mmol) was added to
the organic solution, and the mixture was stirred for 8 h and
then dried over MgSO4. After filtration and removal of solvent,
a brown oil was collected and purified by column chromatog-
raphy (Rf ) 0.30, hexane/ethyl acetate ) 3:1) to give a white
solid (11.6 g, 80%) as the product. Mp: 115-118 °C (CH2Cl2/
hexane). 1H NMR (CDCl3, 250 MHz): δ 1.37 (s, 18 H), 3.81 (s,
6 H), 6.95 (d, 2 H, J ) 8.8 Hz), 7.40 (dd, 2 H, J ) 2.4, 8.8 Hz),
7.78 (s, 2 H), 8.04 (d, 2 H, J ) 2.4 Hz), 8.06 (d, 2 H, J ) 8.5
Hz), 8.20 (d, 2 H, J ) 8.5 Hz). 13C NMR (CDCl3, 75 MHz): δ
31.68, 34.22, 55.94, 111.22, 125.96, 126.84, 127.42, 128.97,
129.74, 135.01, 143.60, 155.13, 157.23. MS (m/e, %, relative
intensity): 504 (M+, 69), 503 (100), 486 (61). HRMS calcd for
C34H36N2O2: 504.2777. Found: 504.2777. IR (neat): 2959, 1586,
1494, 1265 cm-1
.
R ea ct ion s of M2(b b p p )2. The metal dimers
M2(bbpp)2 (M ) Rh, Ir) underwent oxidative addition
with MeI to yield M(bbpp)Me (M ) Rh, 33%; M ) Ir,
36%) and M(bbpp)I (M ) Rh, 25%; M ) Ir, 24%),
respectively, as shown in eq 16.
Rh2(bbpp)2 19b and Ir2(bbpp)2 20b reacted with H2
to produce Rh(bbpp)H 15b and Ir(bbpp)H 16b in 90%
and 85% yield, respectively (eq 12).
Syn t h esis of 2,9-Bis (5-ter t-b u t yl-2-h yd r oxyp h en yl)-
1,10-p h en a n th r olin e, H2bp p (6a ). Pyridine (16 mL) was
placed in a 100 mL two-necked round flask fitted with a
thermometer and a funnel. With rapid stirring concentrated
hydrochloric acid (17.6 mL) was added. The flask was equipped
for distillation, and water was distilled from the mixture until
its internal temperature rose to 210 °C. After cooling to 140
°C, 2,9-bis(5-tert-butyl-2-methoxyphenyl)-1,10-phenanthroline
(6b) was added as a solid, and the reaction flask was fitted
with a reflux condenser connected to a source of nitrogen. The
yellow mixture was stirred and refluxed for 3 h (210 °C). To
the cooled mixture was added water (70 mL), and the solution
was extracted with CHCl3, washed with saturated NaCl
solution, and dried (MgSO4). After removal of solvent, a yellow
solid was collected as the product (4.3 g, 91% yield). Rf ) 0.6
(hexane/ethyl acetate, 1:1). Mp: 150-152 °C (hexane/ethyl
In summary, nonbridged metal dimers of phenan-
throline-based N2O2 ligands of rhodium and iridium
(42) Bakac, A.; Thomas, L. M. Inorg. Chem. 1996, 35, 5880.
(43) J ohnson, S. A.; Hunt, H. R.; Newman, H. M. Inorg. Chem. 1963,
2, 960.
(44) Silverstein, R. M.; Bassler, G. C.; Morrill, T. C. Spectrometric
Identification of Organic Compounds, 4th Edition; J ohn Wiley and
Sons: New York, 1981, p 164.

Rh and Ir Phenanthroline-Based N2O2 Dimers
Organometallics, Vol. 21, No. 13, 2002 2747
1
acetate). H NMR (CDCl3, 300 MHz, ppm): δ 1.40 (s, 18 H),
3 H, J ) 8.5 Hz), 1.33 (s, 18 H), 1.44 (m, 4 H), 1.79 (m, 4 H),
3.35 (t, 4 H, J ) 6.9 Hz), 7.40 (dd, 2 H, J ) 6.9 Hz, 2.2 Hz),
7.68 (s, 2 H), 7.80 (d, 2 H, J ) 2.2 Hz), 8.13 (d, 2 H, J ) 8.8
Hz), 8.27 (d, 2 H, J ) 8.7 Hz), 14.23 (s, 2 H). 13C NMR (CDCl3,
75 MHz): δ 13.78, 21.90, 32.16, 34.33, 34.82, 35.35, 118.85,
119.41, 120.86, 124.13, 126.54, 127.81, 130.57, 138.61, 142.08,
158.34, 158.76. MS (FAB): 588 (M+). HRMS m/e calcd for
7.22 (s, 2 H), 7.44 (s, 2 H), 7.60 (s, 2 H), 7.85 (s, 2 H), 8.07 (d,
2 H, J ) 8.7 Hz), 8.15 (d, 2 H, J ) 8.7 Hz), 14.26 (s, 2 H). 13C
NMR (CDCl3, 75 MHz, ppm): δ 32.22, 34.82, 118.84, 119.30,
120.00, 123.74, 126.41, 127.68, 130.19, 138.04, 141.74, 142.02,
158.66, 158.71. UV-vis (CHCl3, nm, log ꢀ): 364 (4.78). IR (neat
film, cm-1): 3412 (νO-H), 1641, 1540, 1407, 1186, 971, 915, 882.
MS (relative intensity, %): 476 (M+, 92), 461 (98), 445 (26),
433 (13), 405 (14), 377 (5.5), 267 (2.2), 209 (5.6). Anal. Calcd
for C32H32N2O2: C, 80.64; H, 6.77; N, 5.88. Found: C, 80.00;
H, 6.92; N, 5.71.
C
40H48N2O2: 588.3710. Found: 588.3744.
Syn th esis of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
p h en yl)-1,10-p h en a n th r olin e Ch lor id e, Rh (bp p )Cl (8a ).
The ligand H2bpp 6a (100 mg, 0.21 mmol) and RhCl3‚3H2O
(66.3 mg, 0.25 mmol) were added into PhCN (10 mL) and
heated to reflux for 6-8 h under nitrogen. The color of the
solution changed from yellow to red, and an orange precipitate
formed. PhCN was distilled in a vacuum. The residue was
washed with CH2Cl2/hexane (1:1), and an orange solid was
obtained after filtration. The orange solid was put in a Soxlet
extractor and extracted with CH2Cl2/hexane (1:1) to wash away
the remaining ligand. The resulting orange solid was dried
over vacuum at 80 °C for 12 h (54 mg, 42% yield). Rf ) 0.20
Syn t h esis of 5,6-Dib r om o-1,10-p h en a n t h r olin e (7).35
1,10-Phen 4a (0.9 g, 5 mmol) and fuming sulfuric acid
(containing 30% SO3, 7 mL) were loaded into a 15 mL tube.
After the tube was cooled, bromine (0.3 mL, 1 mmol) was added
with a syringe, then the tube was sealed under vacuum. After
it was heated for 12 h at 120 °C in an oil bath, the tube was
broken carefully. The brown solution was poured into ice
water, neutralized with ammonia hydroxide to pH 3, and
filtered, and the yellow solid was recrystallized from ethanol.
5,6-Dibromo-1,10-phenanthroline (7) was obtained in 65%
yield. Rf ) 0.34 (CH2Cl2). Mp: 221-223 °C (CH2Cl2/MeOH)
1
(CH2Cl2/MeOH, 95:5); mp > 350 °C. H NMR (DMSO-d6, 300
MHz): δ 1.36 (s, 18 H), 6.54 (s, 2 H), 7.15 (d, 2 H, J ) 8.1 Hz),
7.36 (d, 2 H, J ) 4.8 Hz), 8.10 (s, 2 H), 8.40 (s, 2 H), 9.08 (s, 2
H). UV-vis (CH2Cl2): 461, 671, 693, 707, 721. MS (FAB,
relative intensity, %): 612 (M+, 55), 577 (99), 562 (49), 547
(19), 477 (27), 307 (11). HRMS m/e calcd for RhC32H30N2O2Cl:
612.1045. Found: 612.1063.
(lit.35 223 °C). H NMR (CDCl3, 300 MHz): δ 7.70 (dd, 2 H, J
1
) 4.2 Hz), 8.74 (dd, 2 H, J ) 1.5 Hz), 9.18 (dd, 2 H, J ) 1.5
Hz). 13C NMR (CDCl3, 75 MHz): δ 124.58, 125.26, 128.69,
137.49, 145.22, 150.96. MS (EI, % relative intensity): 339 (M+
+ 1, 11), 338 (M+, 52), 336 (M+ - 1, 26), 260 (99), 179 (60),
152 (26), 125 (14).
Syn th esis of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
ph en yl)-5,6-di-n -bu tyl-1,10-p h en a n th r olin e Ch lor id e, Rh -
(bbp p )Cl (8b). The ligand H2bbpp 6b (100 mg, 0.17 mmol)
and RhCl3‚3H2O (54 mg, 20 mmol) were added into PhCN (10
mL) and heated to reflux for 6-8 h under nitrogen. The color
of the solution changed from yellow to red, and an orange
precipitate formed. PhCN was distilled off in a vacuum. The
residue was washed with CH2Cl2/hexane (1:1), and an orange
solid was obtained after filtration. The orange solid was put
Syn t h esis of 5,6-Dib u t yl-1,10-p h en a n t h r olin e, P d -
(P P h 3)2Cl2, Ca ta lyzed Rea ction s. To THF (20 mL) saturated
with anhydrous ZnCl2 (11 mmol) at -78 °C was added
dropwise n-BuLi (11 mmol) in hexane. The resulting mixture
was then slowly warmed to room temperature in 2 h to form
BuZnCl. To a suspension of 5,6-dibromo-Phen 7 and Pd(PPh3)2-
Cl2 (10 mol %) in THF (20 mL) was added dropwise BuZnCl
at room temperature. The solution was heated to reflux for
24 h under nitrogen. Water was then added, the layers were
separated, and the aqueous phase was extracted with Et2O.
The combined organic layer was washed with H2O, dried over
MgSO4, filtered, and evaporated to dryness. The residue was
subjected to column chromatography using a hexane/ethyl
acetate (1:1) to give 4b in 28% yield. Rf ) 0.75 (hexane/ethyl
acetate ) 1:1). Mp: 218-220 °C (hexane/ethyl acetate). 1H
NMR (CDCl3, 300 MHz, ppm): δ 0.94 (t, 6 H, J ) 7.3 Hz),
1.46 (m, 4 H), 1.84 (m, 4 H), 3.15 (t, 4 H, J ) 8.0 Hz), 7.45 (dd,
2 H, J ) 4.2 Hz, 3.9 Hz), 8.04 (dd, 2 H, J ) 6.6 Hz, 1.6 Hz),
9.02 (dd, 2 H, J ) 2.8 Hz, 1.6 Hz). 13C NMR (CDCl3, 75 MHz):
δ 13.93, 22.77, 31.79, 39.04, 122.22, 125.29, 126.92, 136.08,
145.20, 163.05. MS (EI, % relative intensity): 295 (M+, 52),
281 (9), 267 (18), 253 (26), 239 (99), 221 (16.2), 195 (42), 183
(71), 149 (35). HRMS m/e calcd for C20H24N2: 292.1939.
Found: 292.1852.
in
a Soxlet extractor and extracted with CH2Cl2/hexane
(1:1) to remove the unreacted ligand. The resulting orange
solid was dried under vacuum at 80 °C for 12 h (44.3 mg, 36%
yield). Rf ) 0.10 (CHCl3). Mp > 350 °C. UV-vis (MeOH, nm):
1
274, 314, 475. H NMR (DMSO-d6, 300 MHz): δ 0.86 (s, 3 H),
1.13 (s, 18 H), 1.34 (s, 4 H), 1.71 (s, 4 H), 2.96 (s, 4 H), 6.60 (s,
2 H), 6.81 (s, 2 H), 7.32 (s, 2 H), 7.54 (s, 2 H), 8.27 (s, 2 H).
UV-vis (MeOH, nm): 274, 314, 475. MS (FAB): 725 (M+).
HRMS m/e calcd for RhC40H46N2O2Cl: 724.2297. Found:
724.2321.
Syn t h esis of Ir id iu m 2,9-Bis(5-ter t-b u t yl-2-h yd r oxy-
ph en yl)-1,10-ph en an th r olin e Car bon yl Ch lor ide, Ir (bpp)-
(CO)Cl (9a ). The ligand H2bpp 6a (100 mg, 0.21 mmol) and
[Ir(COD)Cl]2 (141 mg, 0.21 mmol) were added into xylene, and
the solution was heated to reflux under nitrogen for 26 h. The
color of the solution changed from yellow to red, and a red
precipitate formed. After filtration, a red solid was obtained
(58 mg, 38% yield). Rf ) 0.12 (CH2Cl2/MeOH, 95:5). 1H
NMR (DMSO-d6, 300 MHz): δ 1.32 (s, 18 H), 7.12 (d, 2 H, J )
8.7 Hz), 7.36 (d, 2 H, J ) 6.0 Hz), 8.10 (d, 2 H, J ) 7.5 Hz),
8.20 (s, 2 H), 8.78 (d, 2 H, J ) 9.0 Hz), 8.83 (d, 2 H, J ) 9.0
Hz). IR (KBr): νIr-CO 2049 cm-1. UV-vis (CH2Cl2): 693, 721.
MS (FAB, relative intensity, %): 705 (M+ - CO, 6), 667 (M+
- CO - Cl, 99), 482 (12). HRMS m/e (M+ - CO - Cl) calcd for
IrC32H30N2O2: 665.2007. Found: 665.2047.
Syn th esis of 2,9-Bis(5-ter t-bu tyl-2-h yd r oxyp h en yl)-5,6-
d i-n -bu tyl-1,10-p h en a n th r olin e, H2bbp p (6b). Pyridine (8
mL) was placed in a 100 mL two-necked round flask fitted with
a thermometer and a funnel. With rapid stirring concentrated
hydrochloric acid (8.8 mL) was added. The flask was equipped
for distillation, and water was distilled from the mixture until
its internal temperature rose to 210 °C. After cooling to 140
°C, 2,9-bis(5-tert-butyl-2-methoxyphenyl)-5,6-di-n-butyl-1,10-
phenanthroline (5b) (0.2 g, 0.32 mmol) was added as a solid,
and the reaction flask was fitted with a reflux condenser
connected to a source of nitrogen. The yellow mixture was
stirred and refluxed for 3 h (210 °C). To the cooled mixture
was added water (70 mL), and the solution was extracted with
CHCl3, washed with saturated NaCl solution, and dried
(MgSO4). After removal of solvent, a yellow solid was collected
as the product 6b (0.16 g, 85% yield). Rf ) 0.65 (hexane/EA,
1:1). Mp: 184-186 °C (hexane/ethyl acetate). UV-vis (CHCl3,
nm, log ꢀ) 364 (4.78). IR (neat film) 3408, 2918, 1649, 1568,
Syn t h esis of Ir id iu m 2,9-Bis(5-ter t-b u t yl-2-h yd r oxy-
p h en yl)-5,6-d i-n -b u t yl-1,10-p h en a n t h r olin e Ca r b on yl
Ch lor id e, Ir (bbp p )(CO)Cl (9b). The ligand H2bbpp 6b (100
mg, 0.17 mmol) and [Ir(COD)Cl]2 (126 mg, 0.17 mmol) were
added into xylene, and the solution was heated to reflux under
nitrogen for 24 h. The color of the solution changed from yellow
to red, and a red precipitate formed. After filtration, a red solid
was obtained as the product 9b (48.6 mg, 34% yield). Rf ) 0.10
1
(CHCl3). H NMR (DMSO-d6, 300 MHz): δ 0.91 (t, 6 H, J )
1420, 1266, 883 cm-1. H NMR (CDCl3, 300 MHz): δ 0.87 (t,
7.3 Hz), 1.23 (s, 18 H), 1.38 (m, 4 H), 1.76 (t, 4 H, J ) 6.4 Hz),
1

2748 Organometallics, Vol. 21, No. 13, 2002
Feng and Chan
3.10 (t, 4 H, J ) 8.0 Hz), 6.64 (d, 2 H, J ) 8.0 Hz), 6.77 (d, 2
H, J ) 8.4 Hz), 7.37 (s, 2 H), 7.67 (d, 2 H, J ) 8.1 Hz), 8.38 (d,
2 H, J ) 8.3 Hz). IR (KBr): νIr-CO 2052 cm-1. MS (FAB, %
Rh (bp p )(Me)(P P h 3) (14). PPh3 (2 mg, 7.6 µmol) was added
into Rh(bpp)Me 10a (4.5 mg, 7.6 µmol) in DMSO-d6 (0.4 mL),
and Rh(bpp)(Me)(PPh3) 14 was produced. In the 1H NMR
spectrum, the doublet of Rh-Me changed into a double doublet
at 1.26 ppm with the coupling constants 7.98, 10.36, and 12.24
Hz, respectively. 31P NMR (200 MHz, H3PO4 as the external
standard): δ 47.39 (d, J Rh-P ) 138 Hz). UV-vis (CH2Cl2): 472
nm. MS (FAB, relative intensity, %): 855 (M+ + 1, 4), 854 (M+,
4), 839 (M+ - Me, 98), 593 (M+ - PPh3, 17), 577 (M+ - PPh3
- Me, 16), 562 (36), 522 (9), 456 (2), 414 (7).
relative intensity): 840 (M+, 6). HRMS m/e calcd for IrC41H46
-
N2O3Cl: 840.2797. Found: 840.2753.
Syn th esis of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
p h en yl)-1,10-p h en a n th r olin e Meth yl, Rh (bp p )Me (10a ).
To a suspension of Rh(bpp)Cl 8a (25 mg, 0.0344 mmol) in
EtOH (8 mL) was added N2-purged NaBH4 (3.8 mg, 0.1 mmol)
in NaOH (1 M, 1 mL) through a syringe. The solution was
stirred for 1 h at 50 °C under N2 with the color changing from
red to deep brown. The solution was then cooled to room
temperature. CH3I (0.1 mL, 0.16 mmol) was added through a
syringe. The solution was stirred for 1 h, and H2O (10 mL)
was added. The solution was then extracted with CH2Cl2 (3 ×
20 mL), dried over MgSO4, and evaporated to dryness. The
residue was purified by column chromatography using
CH2Cl2 as the eluent to give the product (10.2 mg, 42%). Rf )
0.45 (ethyl acetate). 1H NMR (DMSO-d6, 300 MHz): δ 0.51
Syn th esis of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
p h en yl)-1,10-p h en a n t h r olin e Isop r op yl, R h (b p p )(iP r )
(11a ). Rh(bpp)Cl 8a (25 mg, 0.040 mmol) was suspended in
EtOH (8 mL). N2 was purged for 10 min. The solution was
then heated to 50 °C, and N2-purged NaBH4 (3.8 mg, 0.1 mmol)
in NaOH (1 M, 1 mL) was added through a syringe. The
solution was stirred for 1 h at 50 °C under N2 with the color
changing from red to deep brown. Then the solution was cooled
to room temperature. 2-Bromopropane (0.1 mL, 0.16 mmol)
was added through a syringe. The solution was stirred for 1
h. Water (10 mL) was added, the reaction mixture was
extracted with CH2Cl2 (3 × 20 mL) and dried (MgSO4), and
the solvent was evaporated off. The residue was purified by
column chromatography using CH2Cl2 as the eluent to give
the product (10.2 mg, 42%). Rf ) 0.75 (ethyl acetate). 1H NMR
(DMSO-d6, 300 MHz): δ -0.55 (1 H, m), -0.07 (d, 6 H, J )
6.6 Hz), 1.36 (s, 18 H), 7.12 (d, 2 H, J ) 6.2 Hz), 7.36 (d, 2 H,
J ) 6.9 Hz), 8.18 (m, 2 H), 8.24 (m, 2 H), 8.79 (s, 4 H). MS
(FAB, relative intensity, %): 621 (M+, 11), 578 (M+ - C3H7,
99). HRMS calcd for RhC35H37N2O2: 620.1904. Found: 620.1888.
Syn t h esis of Ir id iu m 2,9-Bis(5-ter t-b u t yl-2-h yd r oxy-
p h en yl)-1,10-p h en a n th r olin e Meth yl, Ir (bp p )Me (12a ). Ir-
(bpp)(CO)Cl 9a (32 mg, 0.044 mmol) was suspended in EtOH
(8 mL). N2 was purged for 10 min. The solution was then
heated to 50 °C. N2-purged NaBH4 (3.8 mg, 0.1 mmol) in NaOH
(1 M, 1 mL) was added through a syringe. The solution was
stirred for 1 h at 50 °C under N2 with the color changing from
red to deep brown. The solution was then cooled to room
temperature. CH3I (0.1 mL, 0.16 mmol) was added through a
syringe. The solution was stirred for 1 h, water (10 mL) was
added, the reaction mixture was extracted with CH2Cl2 (3 ×
20 mL) and dried (MgSO4), and the solvent was evaporated
off. The residue was purified by column chromatography using
CH2Cl2 as the eluent to give the product (10.0 mg, 34% yield).
Rf ) 0.62 (ethyl acetate). 1H NMR (DMSO-d6, 300 MHz): δ
0.04 (s, 3 H), 1.27 (s, 18 H), 7.15 (d, 2 H, J ) 8.7 Hz), 7.41 (d,
2 H, J ) 8.7 Hz), 7.69 (d, 2 H, J ) 3.0 Hz), 8.24 (2 H, s), 8.84
(s, 2 H), 8.89 (s, 2 H). MS (FAB, relative intensity, %): 682
(M+, 99), 667 (85), 477 (17), 391 (10), 307 (29), 289 (18). HRMS
m/e calcd for IrC33H33N2O2: 680.2142. Found: 680.2165.
Syn t h esis of Ir id iu m 2,9-Bis(5-ter t-b u t yl-2-h yd r oxy-
ph en yl)-1,10-ph en an th r olin e Isopr opyl, Ir (bpp)(iP r ) (13a).
Ir(bpp)(CO)Cl 9a (36 mg, 0.050 mmol) was suspended in EtOH
(8 mL). N2 was purged for 10 min. The solution was then
heated to 50 °C. N2-purged NaBH4 (3.8 mg, 0.1 mmol) in NaOH
(1 M, 1 mL) was added through a syringe. The solution was
stirred for 1 h at 50 °C under N2 with the color changing from
red to deep brown. The solution was then cooled to room
temperature. 2-Bromopropane (0.1 mL, 0.16 mmol) was added
through a syringe. The solution was stirred for 1 h, water (10
mL) was added, the reaction mixture was extracted with CH2-
Cl2 (3 × 20 mL) and dried (MgSO4), and the solvent was
evaporated off. The residue was separated by column chro-
matography using CH2Cl2 as the eluent to give the product
(12.2 mg, 35%). Rf ) 0.72 (ethyl acetate). 1H NMR (DMSO-d6,
300 MHz): δ -0.85 (m, 1 H), -0.67 (d, 6 H, J ) 6.0 Hz), 1.32
(s, 18), 7.51 (d, 2 H, J ) 3.3 Hz), 7.99 (m, 2 H), 8.08 (m, 2 H),
8.36 (m, 2 H), 8.54 (m, 4 H). MS (FAB, relative intensity, %):
653 (M+ - 1, 20), 615 (M+ - C3H7, 4), 461 (M+ - C3H7 - Ir,
9), 281 (42), 207 (39). HRMS M+ - C3H7 m/e calcd for
IrC32H30N2O2: 665.1907. Found: 665.1953.
(d, 3 H, J
) 2.5 Hz), 1.36 (s, 18 H), 7.15 (d, 2 H, J ) 8.8
Rh-H
Hz), 7.38 (dd, 2 H, J ) 2.4 Hz), 8.10 (d, 2 H, J ) 1.8 Hz), 8.14
(d, 2 H, J ) 2.1 Hz), 8.78 (d, 2 H, J ) 5.3 Hz), 8.83 (d, 2 H, J
) 4.9 Hz). 13C NMR (DMSO-d6, 75 MHz): δ 1.54 (d, Rh-CH3,
J Rh-C ) 40.8 Hz), 32.49, 34.85, 118.90, 122.72, 125.12, 125.80,
126.24, 127.49, 130.79, 136.64, 145.89, 153.57, 165.72. UV-
vis (CHCl3): 478 nm. MS (FAB, relative intensity, %): 593
(M+ + 1, 96), 578 (59), 562 (33), 307 (22), 289 (11). HRMS m/e
calcd for RhC33H33N2O2: 592.1591. Found: 592.1528.
Syn th esis of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
p h en yl)-5,6-d i-n -bu tyl-1,10-p h en a n th r olin e Meth yl, Rh -
(bbp p )Me (10b). To a suspension of Rh(bbpp)Cl 8b (25 mg,
0.0345 mmol) in EtOH (8 mL) was added N2-purged NaBH4
(3.8 mg, 0.1 mmol) in NaOH (1 M, 1 mL) through a syringe.
The color of the solution changed from orange to deep brown.
After heating to 50 °C for 1 h, the solution was cooled to room
temperature. CH3I (0.1 mL, 0.16 mmol) was added through a
syringe. The solution was stirred for 1 h, and H2O (10 mL)
was added. The solution was then extracted with CH2Cl2 (3 ×
20 mL), dried over MgSO4, and evaporated to dryness. The
residue was purified by column chromatography using CH2-
Cl2 as the eluent to give the product 10b (13.6 mg, 56%
yield). Rf ) 0.34 (CH2Cl2). UV-vis (MeOH, nm): 410, 474. 1H
NMR (CDCl3, 300 MHz): δ 0.51 (d, 3 H, J ) 2.1 Hz), 0.95 (t,
6 H, J ) 7.3 Hz), 1.44 (m, 4 H), 1.74 (m, 4 h), 3.09 (t, 4 H,
J ) 7.4 Hz), 7.63 (d, 2 H, J ) 6.8 Hz), 7.95 (s, 2 H), 8.22
(d, 2 H, J ) 8.3 Hz), 8.47 (d, 2 H, J ) 8.3 Hz). UV-vis
(MeOH, nm): 410, 474. MS (FAB): 704 (M+). HRMS m/e calcd
for RhC41H49N2O2: 704.2843. Found: 704.2885.
Syn t h esis of Ir id iu m 2,9-Bis(5-ter t-b u t yl-2-h yd r oxy-
p h en yl)-5,6-d i-n -bu tyl-1,10-p h en a n th r olin e Meth yl, Ir -
(bbp p )Me (12b). Ir(bbpp)(CO)Cl 9b (32 mg, 0.038 mmol) was
suspended in EtOH (8 mL). N2 was purged for 10 min. The
solution was then heated to 50 °C. N2-purged NaBH4 (3.8 mg,
0.1 mmol) in NaOH (1 M, 1 mL) was added through a syringe.
The solution was stirred for 1 h under N2 with the color
changing from red to deep brown. The solution was then cooled
to room temperature. CH3I (0.1 mL, 0.16 mmol) was added
through a syringe. After the solution was stirred for 1 h, water
(10 mL) was added and the reaction mixture was extracted
with CH2Cl2 (3 × 20 mL), dried (MgSO4), and evaporated to
dryness. The residue was separated by column chromatogra-
phy using CH2Cl2 as the eluent to give the product 80 (14.8
mg, 49% yield). Rf ) 0.28 (CH2Cl2). 1H NMR (CDCl3, 300
MHz): δ 0.35 (s, 3 H), 0.83 (t, 6 H, J ) 7.3 Hz), 1.25 (s, 18 H),
1.34 (m, 4 H), 1.71 (m, 4 H), 3.09 (t, 4 H, J ) 8.2 Hz), 6.76 (d,
2 H, J ) 7.9 Hz), 6.88 (d, 2 H, J ) 8.4 Hz), 7.48 (s, 4 H), 7.76
(d, 4 H, J ) 7.8 Hz), 8.49 (d, 4 H, J ) 7.8 Hz). MS (FAB, %
relative intensity): 794 (M+, 22). HRMS m/e calcd for
IrC41H49N2O2: 792.3394. Found: 792.3356.
Rea ction of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
p h en yl)-1,10-p h en a n th r olin e Meth yl w ith P P h 3 to give

Rh and Ir Phenanthroline-Based N2O2 Dimers
Organometallics, Vol. 21, No. 13, 2002 2749
Syn th esis of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
p h en yl)-1,10-p h en a n th r olin e Hyd r id e, Rh (bp p )H (15a ).
Rh(bpp)Cl 8a (20 mg, 0.033 mmol) was suspended in EtOH (8
mL). N2 was purged for 10 min. NaBH4 (8 mg, 0.10 mmol) was
dissolved in NaOH (1 M, 1 mL), and N2 was purged for 10
min. Then the NaBH4 solution was added into the above
suspension slowly with a cannula. The solution was stirred
for 1 h at 50 °C under N2 with the color changing from red to
deep brown. The solution was then cooled to room temperature,
and degassed HCl (1 M, 5 mL) was added with a cannula. A
black precipitate was produced immediately. After filtration
under N2, the residue was washed with degassed H2O and
MeOH, then dried under vacuum for 4 h, forming a yellow
solid (14.4 mg, 78% yield). 1H NMR (DMSO-d6, CF3SO3H
added, 300 MHz): δ -22.85 (d, 1 H, J ) 37.3 Hz), 1.49 (s, 18
H), 6.01 (d, 2 H, J ) 5.1 Hz), 7.75 (d, 2 H, J ) 7.8 Hz), 7.87 (d,
2 H, J ) 8.4 Hz), 8.50 (s, 2 H), 8.62 (s, 2 H), 9.22 (s, 2 H). IR
(KBr): νRh-H 2225 cm-1. MS (FAB, % relative intensity): 579
(M+, 59), 578 (M+ - 1, 94), 562 (74), 547 (42), 522 (26), 506
(22).
degassed H2O (3 mL) and MeOH (1 mL), then dried over
vacuum for 4 h to obtain the product 16b (12.6 mg, 62% yield).
1H NMR (DMSO-d6): δ -20.23 (s, 1 H), 0.92 (t, 6 H, J ) 7.3
Hz), 1.24 (s, 18 H), 1.40 (m, 4 H), 1.77 (m, 4 H), 3.02 (t, 4 H,
J ) 7.7 Hz), 6.67 (d, 4 H, J ) 8.5 Hz), 6.88 (d, 4 H, J ) 8.4
Hz), 7.39 (d, 4 H, J ) 2.3 Hz), 7.62 (d, 4 H, J ) 8.3 Hz), 8.35
(d, 4 H, J ) 8.2 Hz). IR (KBr): νIr-H 2046 cm-1. UV-vis
(MeOH, nm): 477.
Reaction of Ir idiu m 2,9-Bis(5-ter t-bu tyl-2-h ydr oxyph en -
yl)-1,10-p h en a n th r olin e Hyd r id e w ith P P h 3. PPh3 (2 mg,
7.6 µmol) was added into a Ir(bpp)H 16a (5 mg, 7.6 µmol)
solution in DMSO-d6 (0.4 mL) under nitrogen, and (bpp)Ir-
1
(H)(PPh3) 17a was obtained. H NMR (DMSO-d6, 300 MHz):
δ -22.45 (d, 1 H, J H-P ) 15.8 Hz). MS (FAB, relative intensity,
%): 930 (M+, 15), 929 (M+ - 1, 23), 667 (M+ - PPh3, 13), 576
(M+ - Ir - PPh3, 15), 518 (17), 475 (14), 383 (15).
Syn th esis of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
p h en yl)-1,10-p h en a n th r olin e Dim er , Rh 2(bp p )2 (19a ). To
Rh(bpp)H 15a (5 mg, 8 mmol) in degassed THF (20 mL) in a
25 mL Schlenk flask was added TEMPO (6 mg, 40 mmol). The
orange color of the solution changed to pale brown im-
mediately. After 2 h, THF, excess TEMPO, and TEMPOH were
removed under high vacuum. The residue was dried for
another 12 h to yield the rhodium dimer 19a (4.5 mg, 95%
Syn th esis of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
p h en yl)-5,6-d i-n -bu tyl-1,10-p h en a n th r olin e Hyd r id e, Rh -
(bbp p )H (15b). Rh(bbpp)Cl 8b (20 mg, 0.028 mmol) was
suspended in EtOH (8 mL). N2 was purged for 10 min. NaBH4
(8 mg, 0.10 mmol) was dissolved in NaOH (1 M, 1 mL), and
N2 was purged for 10 min. Then the NaBH4 solution was added
into the above suspension slowly with a cannula. The solution
was stirred for 1 h under N2 with the color changing from red
to deep brown. The solution was then cooled to room tempera-
ture.Then degassed HCl (1 M, 5 mL) was added with a
cannula, and a black precipitate was produced immediately.
After filtration under N2, the residue was washed with
degassed H2O and MeOH, then dried under vacuum for 4 h,
and a yellow solid was obtained as the product 15b (13.5 mg,
1
yield). H NMR (DMSO-d6, 300 MHz): δ 1.03 (s, 18 H), 1.25
(s, 18 H), 6.30 (s, 4 H), 6.54 (s, 4 H), 6.80 (d, 4 H, J ) 6.6 Hz),
6.90 (d, 4 H, J ) 6.3 Hz), 7.09 (d, 4 H, J ) 7.2 Hz), 7.46 (d, 4
H, J ) 8.4 Hz). UV-vis (MeOH): 379, 392.
Syn th esis of Rh od iu m 2,9-Bis(5-ter t-bu tyl-2-h yd r oxy-
p h en yl)-5,6-d i-n -bu tyl-1,10-p h en a n th r olin e Dim er , Rh 2-
(bbp p )2 (19b). To Rh(bbpp)H 15b (5 mg, 7 mmol) in degassed
THF (10 mL) in a 25 mL Schlenk flask was added TEMPO (6
mg, 40 mmol). The orange color of the solution changed to pale
brown immediately. After 2 h, THF, excess TEMPO, and
TEMPOH were removed under high vacuum. The residue was
dried for a further 12 h to yield the product 19b (4.2 mg, 95%
yield). 1H NMR (CD3OD-d4, 300 MHz): δ 1.02 (t, 12 H, J )
6.8 Hz), 1.31 (s, 18 H), 1.49 (m, 8 H), 1.87 (s, 8 H), 3.23 (t, 8 H,
J ) 7.9 Hz), 6.81 (d, 4 H, J ) 2.8 Hz), 7.07 (d, 4 H, J ) 8.5
Hz), 7.49 (d, 4 H, J ) 8.6 Hz), 7.66 (s, 4 H), 8.12 (d, 4 H, J )
8.2 Hz). UV-vis (MeOH, nm): 466.
1
70% yield). H NMR (DMSO-d6, CF3SO3H added, 300 MHz):
δ -20.27 (d, 1 H, J Rh-H ) 44.4 Hz), 0.91 (t, 6 H, J ) 6.7 Hz),
1.17 (s, 18 H), 1.42 (m, 4 H), 1.66 (m, 4 H), 2.83 (t, 4 H, J )
8.1 Hz), 6.41 (d, 2 H, J ) 10.2 Hz), 6.77 (dd, 2 H, J ) 3.6 Hz),
6.94 (d, 2 H, J ) 8.2 Hz), 7.92 (d, 2 H, J ) 8.1 Hz). IR (KBr):
νRh-H 2226 cm-1. UV-vis (MeOH, nm): 475.
Syn t h esis of Ir id iu m 2,9-Bis(5-ter t-b u t yl-2-h yd r oxy-
p h en yl)-1,10-p h en a n th r olin e Hyd r id e, Ir (bp p )H (16a ). Ir-
(bpp)(CO)Cl 9a (22 mg, 0.030 mmol) was suspended in EtOH
(8 mL). N2 was purged for 10 min. NaBH4 (8 mg, 0.10 mmol)
was dissolved in NaOH (1 M, 1 mL), and N2 was purged for
10 min. The NaBH4 solution was added into the above
suspension slowly with a cannula. The solution was stirred
for 1 h at 50 °C under N2 with the color changing from red to
deep brown. The solution was then cooled to room temperature.
Then degassed HCl (1 M, 5 mL) was added with a cannula,
and a black precipitate was produced immediately. After
filtration under N2, the brown solid was washed with degassed
H2O (3 mL) and MeOH (1 mL), then dried over vacuum for 4
h to obtain the product (10.4 mg, 52% yield). 1H NMR (DMSO-
d6, 300 MHz): δ -22.40 (s, 1 H), 1.32 (s, 18 H), 7.16 (d, 2 H,
J ) 8.7 Hz), 7.37 (d, 2 H, J ) 8.4 Hz), 8.13 (s, 2 H), 8.20 (s, 2
H), 8.80 (s, 4 H). IR (KBr): νIr-H 2046 cm-1. MS (FAB, relative
intensity, %): 668 (M+, 52), 667 (M+ - 1, 96), 477 (M+ - Ir,
25).
Syn t h esis of Ir id iu m 2,9-Bis(5-ter t-b u t yl-2-h yd r oxy-
p h en yl)-5,6-d i-n -bu tyl-1,10-p h en a n th r olin e Hyd r id e, Ir -
(bbp p )H (16b). Ir(bbpp)(CO)Cl 9b (22 mg, 0.026 mmol) was
suspended in EtOH (8 mL). N2 was purged for 10 min. NaBH4
(8 mg, 0.10 mmol) was dissolved in NaOH (1 M, 1 mL), and
N2 was purged for 10 min. Then NaBH4 solution was added
into the above suspension slowly with a cannula. The solution
was stirred for 1 h under N2 with the color changing from red
to deep brown. The solution was then cooled to room temper-
ature. Then degassed HCl (1 M, 5 mL) was added with a
cannula, and a black precipitate was produced immediately.
After filtration under N2, the brown solid was washed with
Syn t h esis of Ir id iu m 2,9-Bis(5-ter t-b u t yl-2-h yd r oxy-
p h en yl)-1,10-p h en a n th r olin e Dim er , Ir 2(bp p )2 (20a ). Ir-
(bpp)H 16a (5 mg, 8 mmol) and TEMPO (6 mg, 40 mmol) were
dissolved in degassed THF (20 mL) in a 25 mL Schlenk flask.
The orange color of the solution changed to pale brown upon
addition of TEMPO. After 4 h, THF, excess TEMPO, and
TEMPOH were removed under high vacuum. The residue was
dried for another 12 h to yield the product 20a (4.2 mg, 92%
1
yield). H NMR (DMSO-d6, 300 MHz): δ 1.39 (s, 36 H), 7.16
(d, 4 H, J ) 8.4 Hz), 7.42 (d, 4 H, J ) 8.0 Hz), 8.24 (s, 8 H),
8.83 (s, 4 H), 8.90 (d, 4 H, J ) 7.4 Hz). MS (L-SIMS): 1334
(M+).
Syn t h esis of Ir id iu m 2,9-Bis(5-ter t-b u t yl-2-h yd r oxy-
p h en yl)-5,6-d i-n -bu tyl-1,10-p h en a n th r olin e Dim er , Ir 2-
(bbp p )2 (20b). Ir(bbpp)H 16b (5 mg, 6 mmol) and TEMPO (5
mg, 33 mmol) were dissolved in degassed THF (10 mL) in a
25 mL Schlenk flask. The orange color of the solution changed
to pale brown when TEMPO was added. After 4 h, THF, excess
TEMPO, and TEMPOH were removed under high vacuum.
The residue was dried for a further 12 h to yield a brown solid
1
as the product 20b (4.0 mg, 90% yield). H NMR (CD3OD-d4,
300 MHz): δ 0.81 (t, 12 H, J ) 7.2 Hz), 1.24 (s, 36 H), 1.31
(m, 8 H), 1.67 (t, 8 H, J ) 7.6 Hz), 3.03 (t, 8 H, J ) 7.7 Hz),
6.75 (d, 4 H, J ) 6.5 Hz), 7.13 (d, 4 H, J ) 8.6 Hz), 7.53 (d, 4
H, J ) 8.3 Hz), 7.71 (s, 4 H), 8.21 (d, 4 H, J ) 8.3 Hz). UV-vis
(MeOH, nm): 475.
Rea ction of Rh 2(bp p )2 w ith Et3SiH a n d CH3I. In a
glovebox, Rh2(bpp)2 19a (4 mg, 3.2 mmol) and Et3SiH or CH3I
(0.11 mL, ∼2.2 mmol) and DMSO-d6 (0.5 mL) were loaded into
a 5 mm diameter NMR tube fitted with a vacuum-line-adapted

2750 Organometallics, Vol. 21, No. 13, 2002
Feng and Chan
Teflon valve. The tube was closed, removed from the glovebox,
degassed by the freeze-pump-thaw method (3 cycles), and
vacuum sealed. The reaction was monitored by 1H NMR. After
about 2 h, the reaction was completed. Rh(bpp)Me 10a : 32%
yield. Rh(bpp)I 21a : 28% yield. Rf ) 0.10 (CHCl3). 1H NMR
(DMSO-d6, 300 MHz): δ 1.19 (s, 18 H), 7.54 (dd, 2 H, J ) 3.0,
5.1 Hz), 7.94 (dd, 2 H, J ) 3.0, 5.7 Hz), 8.12 (s, 2 H), 8.36 (s,
2 H), 8.59 (dd, 2 H, J ) 3.0, 8.8 Hz), 8.77 (d, 2 H, J ) 8.1 Hz).
cycles), and flame-sealed under vacuum. The reaction was
monitored by 1H NMR. After 2 h, the reaction was completed.
Rh(bbpp)Me 12b: 33% yield. Rh(bupp)I 21b: 25% yield. Rf )
0.10 (CH2Cl2). 1H NMR (CD3OD-d4, 300 MHz): δ 1.82 (m, 6
H), 2.27 (m, 4 H), 2.62 (m, 4 H), 3.77 (t, 4 H, J ) 7.5 Hz), 6.47
(d, 2 H, J ) 3.6 Hz), 7.30 (dd, 2 H, J ) 4.5 Hz), 7.85 (d, 2 H,
J ) 3.6 Hz), 8.13 (s, 2 H), 8.73 (s, 2 H). FABMS: 705 (M+).
Ir(bbpp)Me 12b: 36% yield. Ir(bbpp)I 22b: 24% yield. Rf )
0.10 (CH2Cl2). 1H NMR (CD3OD-d4, 300 MHz): δ 0.85 (m, 6
H), 1.32 (m, 4 H), 1.71 (m, 4 H), 3.81 (t, 4 H, J ) 8.1 Hz), 6.90
(dd, 2 H, J ) 2.4, 6.0 Hz), 7.15 (dd, 2 H, J ) 1.5, 7.2 Hz), 7.38
(d, 2 H, J ) 2.7 Hz), 7.70 (d, 2 H, J ) 2.7 Hz), 8.20 (s, 2 H).
FABMS: 905 (M+). The yields were obtained from 1H NMR
integration.
Rea ction of Rh od iu m a n d Ir id iu m 2,9-Bis(5-ter t-bu tyl-
2-h ydr oxyph en yl)-5,6-dibu tyl-1,10-ph en an th r olin e Dim er
w ith H2. H2 was bubbled into solutions of Rh2(bbpp)2 19b (4
mg, 3.0 µmol) and Ir2(bbpp)2 20b (5 mg, 3.0 µmol) in MeOH-
d4 (0.4 mL) under nitrogen, and the reaction was monitored
by 1H NMR. After 2 h, Rh(bbpp)H 15b and Ir(bbpp)H 16b were
obtained in 90% and 85% yield, respectively, from 1H NMR
integration.
MS (FAB, relative intensity, %): 705 (M+ + 1, 1), 577 (M+
-
I, 93). Rh(bpp)H 16a : 36% yield. Rh(bpp)(SiEt3) 23a : 42%
yield, Rf ) 0.50 (CH2Cl2). 1H NMR (DMSO-d6, 300 MHz): δ
0.82 (m, 6 H), 1.07 (m, 9 H), 1.37 (s, 18 H), 7.17 (dd, 2 H, J )
3.3, 8.4 Hz), 7.34 (d, 2 H, J ) 8.1 Hz), 8.12 (s, 2 H), 8.29 (s, 2
H), 8.80 (dd, 4 H, J ) 2.1, 5.4 Hz). MS (FAB, % relative
intensity): 577 (M+ - SiEt3, 20).
Rea ction of Rh od iu m a n d Ir id iu m 2,9-Bis(5-ter t-bu tyl-
2-h yd r oxyp h en yl)-1,10-p h en a n th r olin e Dim er w ith H2.
H2 was bubbled into solutions of Rh2(bpp)2 19a (5 mg, 4 µmol)
and Ir2(bpp)2 20a (5 mg, 4 µmol) in DMSO-d6 (0.4 mL) under
nitrogen, and the reaction was monitored by 1H NMR. After 2
h, Rh(bpp)H 15a and Ir(bpp)H 16a were obtained both in 90%
yields from 1H NMR integration.
Rea ction of M2(bbp p )2 (M ) Rh , Ir ) w ith CH3I. In a
glovebox, M2(bbpp)2 (M ) Rh, 4 mg, 3.0 mmol; M ) Ir, 5 mg,
3.0 mmol), CH3I (0.11 mL), and MeOH-d4 (0.5 mL) were loaded
into a 5 mm diameter NMR tube fitted with a vacuum-line-
adapted Teflon valve. The tube was closed, removed from the
glovebox, degassed by the freeze-pump-thaw method (3
Ack n ow led gm en t. We thank the Direct Grant of
the Chinese University of Hong Kong for financial
support.
OM010903G